JPS5839177A - Recording device - Google Patents

Abstract

PURPOSE:To make recording and reproducing of an audio signal possible even when a tape speed is lowered, and to eliminate the beat interference caused when recording and reproducing, by subjecting the audio signal to pulse amplitude modulation and superposing this signal to the horizontal synchronizing signal of a video signal. CONSTITUTION:Only the luminance signal of the video signal inputted from an input terminal 1 is separated by an LPF 4. This luminance signal is clamped, and a synchronizing signal is separated by a synchronizing signal separating circuit 10. This separated synchronizing signal becomes sampling pulse having a constant pulse width through monostable multivibrators 11 and 12 and is sent to a sampling circuit 13. Meanwhile, the audio signal passes through an AGC circuit 14 and is gated in the sampling circuit 13 to become a PAM signal, and this signal gates the horizontal synchronizing signal part of the video signal clamped by a gate circuit 6. As the result, a signal where the PAM audio signal is inserted to the horizontal synchronizing signal is obtained and is subjected to FM modulation and is applied to a recording head.

Description

[Detailed description of the invention] The present invention relates to a recording device for recording video signals.

In helical VTRs, which perform FM modulation on the video signal, low-frequency conversion on the color signal, and mix and record the signals, the tape speed is slowed down to extend the recording time. Recording and playback in the DIO band is becoming difficult.

As a countermeasure to this problem, there are methods that record the audio by FM modulating it and mixing it with the video signal, and using PAM (Pulse Amplitude Modulation), which modulates the horizontal synchronization signal as proposed in Japanese Patent Publication No. 33-3811.
There were methods for recording by performing modulation such as PWM (Pulse Width Modulation) and PTM (Time Division Modulation), but the former required complicated circuits and was difficult to combine the carrier wave of the audio signal and the low-frequency converted color signal. There are problems due to beats, etc., and in the latter case, when trying to increase the dynamic range of audio, the peak-to-peak value of the video signal increases, resulting in a wide band during FM modulation.

In view of the above points, the present invention provides an improved recording device.

Another object of the present invention is to provide a recording device that records an audio signal in a horizontally synchronized manner with a video signal.

Another object of the present invention is to provide a recording device that performs pulse amplitude modulation on an audio signal and records the modulated audio signal superimposed on a horizontal synchronization signal of a video signal.

Other objects of the present invention will become clear from the following description of embodiments with reference to the drawings.

An embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3.

FIG. 1 shows the recording system, FIG. 2 shows the reproduction system, and FIG. 3 shows the waveforms of each part. Note that the color signals are omitted. In Figure 1, 1
is the video signal input terminal, 2 is the audio input terminal, 3 is A
Go, a low-pass filter (L
, P, F, ), 5 is a 2-amp circuit, 6 is a gate circuit that inserts a pulse amplitude modified ml (PAM) signal into the horizontal synchronization signal, 7 is an FM modulation circuit for the luminance signal, 8 is a recording amplifier, 9#i Head for recording signals on tape, 10
11 and 12 are a synchronous separation circuit, 11 and 12 are monomultis that generate sampling pulses, 13 is a sampling circuit that PAMs audio signals with sampling pulses, and 14 AGO circuits. In the reproduction system 82 diagram, 15 is a reproduction amplifier that amplifies the reproduction output from the tene, 16 is a 9M demodulator, 17 is a clamp circuit, and 181 is a PA inserted into the horizontal synchronization signal.
A gate circuit removes the M signal and restores the normal horizontal synchronization signal, 19d is a synchronization separation circuit, 20. 21 is a monomulti that generates a sampling pulse to gate the audio signal inserted into the horizontal synchronization signal, 22 is a gate circuit, 23 is a circuit that holds the peak value of the sampled audio signal, and 24 is a low-pass filter (L, P, F, ) that returns the PAM signal to the original signal.

The operation of the above configuration will be explained.

During recording, the video signal input from terminal L is P and F.

4, only the n-degree signal is separated. The luminance signal is clamped and a synchronization signal is separated by a synchronization separation circuit 10. The waveform at that time is shown in Figure 3B. Furthermore, Monomulti 11.1
2, an electric pulse--sampling pulse as shown in FIG. 3 is generated and sent to the sampling circuit 13. On the other hand, the audio signal passes through the AGO circuit 14 and is gated by the C sampling pulse in the sampling circuit to become a PAM signal. In other words, the audio signal is sampled at the horizontal frequency, and the waveform at that time is shown as EVC.

The PAM audio signal is clamped by the gate circuit 6 and the horizontal synchronization signal part of the nine-way signal is clamped.As a result, the PAM audio signal is inserted (or superimposed) into the horizontal synchronization signal as shown below. ) becomes a signal. The signal is further FM modulated. By suppressing the audio dynamic range, that is, the peak-to-peak value of the PAM signal, to the peak-to-peak value of the video signal, a sufficient dynamic range can be obtained without requiring a wide fiFM waveband. , the FM modulated signal is amplified by a recording amplifier and recorded on a tape by a head.

Next, the time of reproduction will be explained. The signal reproduced by the head is amplified by a reproduction amplifier 15 and FM demodulated. FM
The demodulated signal is guided on one side to a clamp circuit 17 and on the other to a synchronous separation circuit 19. The synchronized and separated signal B is converted into a waveform C using a monomulti, gates the PAM signal part of the clamped video signal, holds its peak value in a hold circuit 23, and then outputs the signal to LP and F.

24, the original audio signal is restored.

The sampling frequency is, for example, 15.75 KHz.From the rounding sampling theorem, the theoretical value after demodulation is 7 KHz.
This means that it can be restored to a certain extent, which would be sufficient for general conversation. However, music etc. (Example in case the band is widened and rounded! Figure 4.

It is shown in FIGS. 5 and 6.

The same blocks as in FIGS. 1 and 2 are indicated by the same numbers.

Figure 4 shows the recording system. 27.2g, 29°30 is PA
31 is an OR circuit, 32 is a mono multi that causes a certain delay from the horizontal synchronization signal, 33 is duty 5.
The circuit that consists of a mono multi that is set to 09g, a mono multi of 34.36, an inverter of 35, and an OR circuit of 37 is a circuit that creates a pulse that samples the audio ministry code at twice the horizontal frequency, and 38 is a bucket pregate. 39 is an inverter, and 40 is a bucket pre-gate device (BBD) that compresses the PAM signal.

@Figure 5 is the reproduction system.

41.42 is a monomulti that creates a pulse to gate the PAM signal inserted into the horizontal synchronization signal, 43.44, 45.
The circuit consisting of 47 monomulti, 46 inverter, and 48 OR circuit is a circuit that generates a pulse with twice the horizontal frequency with a certain phase shift from the horizontal synchronization signal, 49 is an OR circuit that generates a clock for BBD51, and 50 is an inverter. , 51 indicates a bucket pregate (BBD) circuit that decompresses the compressed PAM signal.

Next, the operation will be explained.

During recording, the luminance signals separated into L, P, P, and 4 are separated into synchronization signals by a clamp circuit 5 and a synchronization separation circuit IO. The monomulti 27, 28, 29° 30 creates two pulses that exist within the horizontal synchronizing signal section. The waveform at that time is shown in FIG. 6fK.

The synchronization signal is sent to the monomulti 32 and delayed by a certain phase. Further, the monomulti 33 converts the duty-50X1 frequency into a horizontal frequency signal. A gate pulse is used to send the pulse and the pulse passed through the inverter 35 to the 34 monomulti 36, respectively. Therefore, the output of the OR circuit 37 is a sampling pulse having twice the horizontal frequency as shown in FIG. 6C. The audio signal passing through the AGO circuit 3 is sampled by the signal O in FIG. 6 and becomes a PAM signal at t46.

On the other hand, the signals f and c in FIG. 6 are led to the OR circuit 38, and the clock pulse in FIG. 6 Figure C P
The AM audio signal is compressed so that two signals are included in each horizontal synchronization signal period, such as N. The signal shown in Figure 6 is also clamped and gates the horizontal sync signal portion of the video signal to create a waveform in which the PA Ni audio signal is inserted within the horizontal sync signal as shown in Figure 6i. Figure 6i
The signal indicated by K is FM modulated by an Ii'M modulator 7, amplified by a recording amplifier 8, and recorded on a tape by a head 9.

Next, the time of reproduction will be explained. The reproduced output is amplified by a reproduction a/b 15, FM demodulated by an FM demodulator 16, and restored to a signal as shown in FIG. 6i. The signal shown in FIG. 6i is synchronously separated to become the signal shown in FIG. 6S, and the signal y is sent to the monomulti 43. mono multi 43
The signal shown in FIG. 6, which is sent to
, the OR circuit 48 generates a pulse train (signal shown by cK in Figure 1) whose frequency is twice the horizontal frequency. On the other hand, the signal shown in Figure 6 C sent to the monomulti 41 is delayed by a certain phase, and a gate pulse is created in the monomulti 42, which is the PAM signal of the clamped Eishun signal (signal shown in Figure 6 i). ,
is gated by the gate 22, resulting in the signal shown in the sixth diagram. The signal shown in FIG. 6 hK and the signal shown in FIG.
Through this, a clock pulse for driving the BBD as shown in Figure tJX6 is created. This pulse and this in/(-
By driving the BBD with the pulse passed at 50, the signal shown in FIG. 6 is expanded to the original PAM signal (FIG. 6e). The peak value of the expanded PAM audio signal is held, and the original continuous audio signal (FIG. 6d) is restored by P, F, 24.

According to this embodiment, the sampling frequency is twice the horizontal frequency, so the band that can be reproduced after L, P, F is half that, for example, about 15 KHz, even if the source of music etc. is busy. Sufficient bandwidth can be obtained. In addition, according to this embodiment, a monomulti was used to obtain twice the horizontal frequency, but to further improve the accuracy, a commonly used multiplier or v
oo, phase comparison a, L, P, F, equal caranal P L
A multiplier or the like having an L configuration may be used.

As described above, according to the present invention, the following effects can be improved.

0 Even when the tape speed is slow and it is impossible to record/play back the audio signal, recording/playback is possible by inserting the horizontal synchronization signal of the video signal and the internal pressure audio signal.

0 No need for a fixed head dedicated to audio.

0 There is no beat interference, which is a problem when an audio signal is tuned to FMi and multiplexed with FM, a modified luminance signal, and a low frequency converted color signal for recording and playback.

0 The deviation of FM modulation can be narrowed compared to 1 case where the horizontal synchronization signal is PAMed. It also allows for a large dynamic range.

0 If you sample the audio signal at twice the water frequency, you will get a more sufficient bandwidth than K.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a recording device to show an embodiment of the present invention, FIG. 2 is a block diagram of a playback device to show an embodiment of the invention, and FIGS. 3A to 3F are timing charts. FIG. 4 is a block diagram of a recording device showing another embodiment of the invention, FIG. 5 is a block diagram of another reproduction device showing another embodiment of the invention, and FIG. 6 is a timing chart. . 6...Gate circuit 13...Sampling circuit

Claims (3)

[Claims] (1) A recording device having means for superimposing an audio signal on a horizontal synchronization signal of a video signal by pulse amplitude modulation. (2) The recording device according to claim 1, further comprising means for sampling the audio signal at a horizontal synchronization frequency. (3) Claim 1, further comprising means for sampling the audio signal at a horizontal frequency N times higher, compressing the sampled audio signal, and superimposing it on a horizontal synchronization signal.
Recording device as described in section.